A heat pump outdoor unit for performing hot-water supply or a cooling/heating operation includes a system using a plate heat exchanger as a condenser and a subcooler. Examples of the plate heat exchanger include a plate heat exchanger serving as both a condenser and a subcooler. For example, in a proposed plate heat exchanger, a boundary plate is provided in a heat transfer unit to define two heat exchange units (a condensation unit and a subcooling unit) (see, for example, Patent Literature 1).